Danny, I support the use of energy/money efficient designs. I like the idea of basically an intake snorkel design for your clothes dryer. Besides the money factor of not drawing in more unwanted outside air but in the summer the incoming air is pre-heated. As long as it is hotter outside your house you will get this benefit.
I'm not crazy about the idea of cutting another 4" hole in the side of my house, so you should run the intake air and the outflowing through a heat exchanger which could be easily fit between the drum and the body of the dryer. That feature would most likely make me happy to cut another hole in my house.
Actually there have been a few heat exchanger ideas patented. Most of them are huge contraptions.
From a safety standpoint there will most likely be another hole cut. There are already enough clothes dryer fires every year due to airflow issues. Trying to take air in, as well as pushing air out, from the same hose would probably increase the fire dangers associated with airflow.
It may just be me, but I think when folks actually learn of the huge amounts of air being pumped out of their homes, another small hole won't be such an issue. Also the air source for the present dryer design wasn't discussed much on the contest application due to the 500-word limit.
On a typical single story home the majority of the air that is vacuumed into the home is from the attic. You just wouldn't believe how "porous" your ceiling is with all of the penetrations for lights, ceiling fans, HVAC vents, smoke alarms, bath exhaust vents, etc. In the summer you have potentially 135-degree air being vacuumed right out of the attic and into your home due to drying clothes. Not only do clothes dryers cause this negative pressure situation, but bath exhaust fans and vent-hoods do as well. However the dryer is the monster vacuum compared to the others, and the one with the most hours of use over time.
If you had zero air flow coming into the home the HVAC would have a much easier time keeping the temperature one or two degrees either side of your temperature setting. But when you introduce 135-degree attic air in the summer, or freezing cold air in the winter, you just increased the load on your HVAC system in a very big way.
For anyone who doesn't know what HVAC stands for, that is Heating Ventilating and Air-Conditioning, or another words our central air-condition system.
Some sort of heat exchanger would be nice, but the real focus of my dryer design is saving heating and cooling energy, and not so much the energy use of the dryer itself.